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SUMMARY:Droplet splashing - Michael Brenner\, Harvard University
DTSTART:20140610T120000Z
DTEND:20140610T130000Z
UID:TALK52824@talks.cam.ac.uk
CONTACT:Dr C. P.  Caulfield
DESCRIPTION:When a droplet of fluid hits a solid surface at high speed\, c
 ommon experience dictates that it leads to a spray of droplets. I will dis
 cuss our recent efforts to develop a first principles\, mathematical descr
 iption of the events leading to droplet splashing on a solid surface--and 
 will argue that the essence of the phenomenon arises because of a singular
 ity that occurs in the equations of motion before the droplet contacts the
  surface. Experiments have long showed that the most violent splashes are 
 preceded by the ejection of a very thin fluid sheet from the vicinity of t
 he contact point\, though the fluid mechanical origin of this sheet has be
 en completely unclear. From simulations and an asymptotic discussion begin
 ning from the Navier Stokes equation\, we demonstrate that the sheet origi
 nates before the droplet contacts the solid surface\,and give detailed pre
 dictions for the characteristics of the sheet (thickness\, speed\, velocit
 y). For a ~ 1mm droplet thrown at a surface at a few meters per second\, t
 he sheet ejects upwards at 100m/sec when the droplet is 10s of nanometers 
 from the solid surface. Recent experiments probing these predictions will 
 also be described. Finally we will discuss our current confusions regardin
 g the effects of liquid viscosity.
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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